1. Field of the Invention
The invention relates to chemical etching of material, often from a substrate, as practiced in varied fields including the manufacture of printed circuits and the like.
2. Description of the Prior Art
There has been increasing concern in the etching industry about the level of etched material in the rinse water of an etching machine, and the resultant pollution of bodies of water. When ion exchange is used to remove such material from rinse water, a serious problem arises. The material that remains in the ion exchanger must be removed in order to regenerate the ion exchanger for further use. The regeneration of ion exchangers has traditionally been accomplished by employing a sodium hydroxide or sodium chloride (brine) aqueous backwash. This backwash liquor, after regeneration, contains the material that was removed from the rinse water. Thus, the problem remains of the disposing of the contaminated backwash liquor. This solution now contains a pollutant and must either be hauled away or the pollutant chemically precipitated. Such a system obviously is not practical and has not been generally employed in the etching industry. In addition, some commercial ion exchange substances for specialized applications are difficult to regenerate, and typically must be rinsed with hydrochloric acid solution and then neutralized with sodium hydroxide solution. This process generates large quantities of contaminated hydrochloric acid and sodium hydroxide solutions, and is obviously not acceptable.